The present invention relates to a battery with a spare battery.
As a countermeasure to prevent against battery depletion due to negligently not switching off a load, such as a lamp switch of an automobile, there is a method in which a spare battery included with a main battery is charged, so that, for example, in the event of main battery failure, an engine can be started. To accomplish such an object, a so-called switch battery was developed in which a main battery and a spare battery are used so that the circuit can be changed in case of emergency. However, since the switch battery uses the main battery and the spare battery, thereby requiring a charger for the spare battery and complicating the circuit connection, it did not gain public attention. Currently, switch batteries having a main battery using six cells and a spare battery using six cells housed in a package are on the market of European countries and the United States. However, the size of this switch battery is the same as that of a conventional 6-cell type battery due to the necessity of compatibility with the conventional 6-cell type battery. Consequently, the main battery is small, and so has a capacity that is approximately 60 to 70% of that of the conventional 6-cell type battery, and a life that is approximately 20 to 30% shorter than that of the conventional battery. Therefore, even though the switch battery seems to offer an excellent advantage in an emergency, it has not been widely used due to disadvantages of small capacity and short life.